Question

Radio signals travel at a rate of 3x10^8 meter per second. How many seconds would it take for a radio signal to travel from a satellite to the surface of Earth if the satellite is orbiting at a height of 9.6*10^6 meters? ( Hint: Time divide by speed.)
A) 3.2*10^2 seconds
B) 3.2*10^-2 seconds
C) 3.13 *10^1seconds
D) 2.88*10^15 seconds

Answer 1

Our satellite is at a distance (from Earth) of $9.6 * 10^6$ meters. Since:

$speed = \frac{distance}{time}$

Solving for time:

$speed * time = \frac{distance}{time} * time$

The time's on the right cancel, so we are left with

$speed * time = distance$

We then divide both sides by speed:

$\frac{speed * time}{speed} = \frac{distance}{speed}$

Now the speed's on the left cancel, and we are left with:

$time = \frac{distance}{speed}$

Now we plug in our numbers for speed and distance: